Preloading custom data and fields in the topic list

[angus (Angus McLeod)]

Just for anyone reading this in 2025 I’ve written an updated version on the same topic

Preloading data and dealing with N+1 Query problems

When working with the Discourse rails application, whether building a plugin, or making a pull request to discourse/discourse there are a number of contexts where you’ll encounter N+1 query problems. This topic explains how to handle data preloading to address such problems and keep Discourse performant. N+1 Query Problems in Rails First, if you’re not already familiar with N+1 query problems, and how Rails addresses them, check out this section of the guides. Topics The N+1 issues to look ou…